Field of the Invention
The present invention relates to an image processing apparatus, especially to a distortion correction when an image changes continuously.
Description of the Related Art
Various kinds of methods are disclosed for applying a lens optical correction such as distortion correction to a digital single-lens camera, which has an interchangeable lens. For example, Japanese Patent Laid-open No. 2003-219246 discloses a method that stores a distortion correction amount for each zoom position, acquires a zoom position at image capturing, acquires a correction amount for the zoom position, and applies a correction. Japanese Patent Laid-open No. 2005-57605 discloses another method that stores a distortion correction amount for each zoom position, calculates a distortion correction amount through an interpolation process when no distortion correction amount is stored for a zoom position at image capturing, and applies a correction.
Since the lens of the digital single-lens camera is interchangeable, it is difficult to store, in the digital single-lens camera, distortion correction coefficients for all lenses. Thus, it is required to calculate a necessary distortion correction coefficient when needed before applying a distortion correction. When a lens optical correction is preformed at still image capturing, there is time to calculate a distortion correction coefficient and apply a correction after an image capturing instruction (command) is received from the user of the digital single-lens camera. However, when an image changes continuously during, for example, a live view and moving image capturing, there is likely to be no time to calculate the distortion correction coefficient in accordance with a zoom change and apply a correction. For this reason, the distortion correction is likely to be applied with a delay from the zoom change at live view image capturing through the digital single-lens camera.